Rail vehicle disc brake arrangement

ABSTRACT

A rail vehicle disc brake arrangement includes a yoke (1) with a brake cylinder (11) and a slack adjuster (16). In order to obtain advantages as regards design, function and space requirements the yoke (1) comprises two telescoping yoke parts: a fixed part (4) and a movable part (5). The slack adjuster (16) is arranged to act between these two parts. The brake cylinder (11) on the movable yoke part is connected to a yoke lever (6), which is pivotally attached to the movable part, has a pad holder (8) with a brake pad (9), and controls the slack adjuster (16).

TECHNICAL FIELD

This invention relates to a rail vehicle disc brake arrangement,including a disc brake yoke to be suspended from an underframe or bogieof the vehicle in the vicinity of the disc or discs to be braked, theyoke being provided with a fluid operated brake cylinder, a slackadjuster, and associated pad holders with brake pads on either side ofthe disc or discs.

BACKGROUND ART

Most disc brake arrangements for rail vehicles are of a type in the artusually referred to as the caliper type and having two legs connected toeach other at an intermediate portion. The free end of each leg isprovided with a pad holder and a brake pad, whereas the opposite endsthereof are actuated by a brake cylinder often incorporating a built-inslack adjuster. The slack adjuster may, however, in certain cases bearranged somewhere else in the disc brake arrangement, for example asshown in U.S. Pat. No. 3,645,364, where it constitutes the connectionlink between the two legs or levers of the caliper.

Although many intermediate variations may be found a second but stillless usual main type of rail vehicle disc brake arrangement is the yoketype, where a substantially stiff yoke extends around the disc to bebraked and a brake force is applied from said yoke, for example by meansof a brake cylinder on the yoke at the disc. A relatively recent andtypical example of such an arrangement is shown in GB No. 2 018 918 butalso GB No. 1 236 877 is illustrative.

The known arrangements suffer from different disadvantages, some of themhaving regard to specific applications, and it is of utmost importanceto improve the versatility of the arrangement so as to allow the use ofa certain arrangement with only relatively minor modifications for agreat variety of applications. In other words: it is desirable to obtainan arrangement consisting of relatively few interchangeable componentsusable for a great variety of applications on different kinds ofvehicles and bogies with a low space requirement, low price, lowmaintenance cost and so on.

THE INVENTION

All the different requirements are according to the invention fulfilledand the disadvantages with prior arrangements obviated if the slackadjuster is arranged to act between two telescoping yoke parts--a fixedpart and a movable part--of which the yoke is comprised, if one padholder with its brake pad, in a way known per se, is arranged on thefixed yoke part, and if a yoke lever with the second pad holder and itsbrake pad is pivotally attached at an intermediate portion thereof tothe movable yoke part, is connected to the brake cylinder mounted on themovable yoke part, and is arranged to control the slack adjuster.

If the available space axially from the disc is limited, which it oftenis, and if a force amplification from the brake cylinder is desirable,the brake cylinder may be connected to the yoke lever at its endopposite to the pad holder and brake pad, the yoke lever thus acting asa force transmitting means.

In such a case the slack adjuster preferably is of the axial type, isarranged within the yoke, is attached to the movable yoke part and isanchored to the fixed yoke part, the yoke lever coacting with a controlmember protruding from the slack adjuster.

In a modified embodiment, which is of special interest if it is desiredto use a well tested and comparatively cheap slack adjuster made in verylarge series, the slack adjuster is of the automatic brake lever type,primarily intended for automotive S-cam drum brakes, is attached on themovable yoke part, and with its outgoing work wheel is connected to acam-shaft, which is rotatably arranged in the movable yoke part and hasa cam engaging a corresponding hole in the fixed yoke part.

In such a case a control arm of the automatic brake lever may beconnected to a transmission arm pivotally attached to the yoke lever.

If there is more space axially than radially around the disc and ifother special requirements are to be fulfilled, the brake cylinder maybe connected to the yoke lever at its connection to the pad holder withits brake pad, the opposite arm of the lever acting as a control meansfor the slack adjuster.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail below reference beingmade to the accompanying drawings, in which

FIG. 1 is a perspective view of a rail vehicle disc brake arrangementaccording to the invention,

FIG. 2 is a partly sectional plan view of a disc brake arrangement verysimilar to the one shown in FIG. 1,

FIGS. 3 and 4 are a plan view and a side view respectively of a secondembodiment of the invention, and

FIGS. 5 and 6 are a partly sectional plan view and a side viewrespectively of a third embodiment of the invention.

DETAILED DESCRIPTION OF THREE EMBODIMENTS

A perspective view of a first embodiment of a rail vehicle disc brakearrangement is shown in FIG. 1, whereas a mainly sectional plan view ofa closely similar embodiment is shown in FIG. 2. These two figures willbe regarded as showing the same embodiment, and the same referencenumerals will thus be used.

At the outset it may be noted that the first embodiment shown in FIGS. 1and 2 is illustrated as intended for cooperation with wheel-mountedbrake discs, whereas the two remaining embodiments are illustratedtogether with axle-mounted discs; however, only minor modifications arenecessary for using either disc type for any embodiment.

Also, suspensions for the different disc brake arrangements are onlysuggested; any suitable type of suspension may be used and the chosensuspension does not form any part of the invention.

Referring now to FIGS. 1 and 2 a two-part disc brake yoke 1 is to besuspended from a rail vehicle underframe or bogie in any suitable way inthe vicinity of a wheel 2 with wheel discs 3 attached thereto.

The yoke 1 comprises two telescoping parts 4 and 5, of which the onenearest to the viewer in FIG. 1 or the lower one in FIG. 2 may be calledthe fixed yoke part 4 and thus the second one the movable yoke part 5.

A yoke lever 6 is at an intermediate portion pivotally attached to themovable yoke part 5 at 7. A pad holder 8 with a brake pad 9 is pivotallyattached to one end of the yoke lever 6, whose opposite end is pivotallyattached to a piston rod 10 of a (pneumatic) brake cylinder 11, which ismounted on a bracket 12 bolted to the movable yoke part 5.

A pad holder 13 corresponding to the pad holder 8 is attached to thefixed yoke part 4 and is likewise provided with a brake pad 14.

As shown in FIG. 1 the movable yoke part 5 and the two pad holders 8 and13 are provided with suspension attachments 15 (of which the one on thepad holder 8 is not visible) for the suspension of the arrangement froma vehicle underframe or bogie by means of not shown suspension links orthe like.

A slack adjuster 16 is provided between or inside the two yoke parts 4and 5. The purpose of this slack adjuster 16, whose design and functionis not material to the present invention and will not be furtherdescribed, is to adjust the position of the movable yoke part 5 relativeto the fixed yoke part 4 or in other words the width of the yoke 1depending on the wear of the brake pads 9 and 14 so as to keep therelative angular position of the yoke lever 6 or the stroke of thepiston rod 10 constant irrespective of the pad wear.

The slack adjuster 16 is at 17 attached to the movable yoke part 5, andits end is anchored to the fixed part 4 by means of a screw head 18.There is a serrated cone clutch between the fixed yoke part 4 and thescrew head 18 for normally preventing relative rotation but for allowingmanual adjustment from the outside provided that the resistance of theclutch is overcome.

A control member 19 on the slack adjuster 16 cooperates with yoke lever6 for giving the necessary control signal to the slack adjuster, if at abrake application the angular movement of the yoke lever should beexcessive indicating excessive wear of the brake pads 9 and 14.

A spring 20 is provided between the fixed member 4 and the slackadjuster 16 (or thus the movable member 5) so as to prevent rattle andundesired noise between the parts.

A second embodiment of a disc brake arrangement according to theinvention is shown in FIGS. 3 and 4. The only essential differencecompared to the FIGS. 1 and 2 embodiment is the type of slack adjusteremployed.

Also in this embodiment a disc brake yoke 30 consists of two telescopingparts - a fixed part 31 and a movable part 32. A yoke lever 33 (in thiscase consisting of a pair of arms as shown in FIG. 4) is pivotallyattached to the movable yoke part 32 at 34. The end of this lever 33 ispivotally connected to the piston rod 35 of a brake cylinder 36 mountedon a bracket 37, which is attached to the movable yoke part 32.

A pad holder 38 with a brake pad 39 is attached to the fixed yoke part31, whereas a pad holder 40 with a brake pad 41 is attached to the yokelever 33 at 42.

The two brake pads 39 and 41 are arranged to coact with an axle-mountedbrake disc 43, but as earlier stated only minor modifications arenecessary for adopting the shown brake arrangement for use withwheel-mounted brake discs.

The brake arrangement is to be suspended from a vehicle underframe orbogie in a way corresponding to the first embodiment; only a suspensionattachment 44 on the pad holder 40 is shown.

The slack adjusting function is in this case performed by a slackadjuster especially well known in the automotive brake art as anautomatic brake lever, which is normally used as a brake forcetransmitting and slack adjusting lever in an S-cam drum brake system forheavy road vehicles, such as trucks and buses. Such a slack adjuster isdescribed in U.S. Pat. No. 3,692,152 issued Sep. 19, 1972 to K. B.Larsson.

For the proper understanding of the invention and the function of thedisc brake arrangement it is not necessary to have any knowledge aboutthe design and function of the automatic brake lever used; nodescription thereof is thus offered here.

An automatic brake lever 45 of the specified type is thus fixedlymounted on the movable yoke part 32 by means of a bolt 46 and is--bymeans of its outgoing worm wheel 47--attached to a camshaft 48 rotatablymounted in the movable yoke part 32.

An outgoing control arm 49 of the brake lever 45 is coupled to atransmission arm 50, which is pivotally attached to the yoke lever 33.

A cam 51 of the cam-shaft 48 extends into a correspondingly shaped holein the fixed yoke part 31, so that a relative sliding or telescopingmotion between the two yoke parts 31 and 32 is obtained at a rotationalmovement of the worm wheel 47 in the brake lever 45 or thus of thecamshaft 48. Such rotational movement will be obtained during a brakeoperation under the action of the brake cylinder 36, if a controlmovement transmitted to the slack adjusting mechanism in the automaticbrake lever 45 via the transmission arm 50 and the control arm 49indicates that excessive wear of the brake pads 39 and 41 has occured.The result of said rotational movement is that the total width of theyoke 30 is diminished.

Manual adjustment of the brake lever 45 and thus of the width of theyoke 30 is possible by means of a manual adjustment screw 52 on thebrake lever 45.

A possible modification of the embodiment shown in FIGS. 3 and 4 is toreplace the cam-shaft and and cam arrangement 48, 51 with a rack andpinion arrangement between the two yoke parts 31 and 32.

A third embodiment, only slightly differing from the first embodimentshown in FIGS. 1 and 2, is shown in FIGS. 5 and 6.

Also in this case a disc brake yoke 60 consists of two telescopingparts--a fixed part 61 and a movable part 62. A yoke lever 63 (or rathera pair of yoke levers) is pivotally attached to the movable yoke part 62at 64. The movable yoke part 62 is provided with an integral bracket 65for a brake cylinder 66, preferably a hydraulic brake cylinder, whosepiston rod 67 is connected to the yoke lever 63 and a pad holder 68 witha brake pad 69.

A corresponding pad holder 70 with a brake pad 71 is attached to thefixed yoke part 61. Both brake pads 69, 71 are arranged to cooperatewith a brake disc 72, and the whole disc brake arrangement is suspendedfrom the vehicle underframe or bogie in any conventional, not shown way.

A slack adjuster 73 of the same type as the one used in the embodimentshown in FIGS. 1 and 2 is provided between the two yoke parts 61 and 62.The adjuster 73 is thus attached to the movable yoke part 62 at 74 andhas its end anchored to the fixed part by means of a screw head 75allowing manual adjustment of the adjuster.

A control rod 76 is connected on the one hand to the yoke lever 63 at 77and on the other hand to the adjuster 73 at 78. In the same manner as inthe two other embodiments the purpose of the slack adjuster is todiminish the width of the yoke 60 at the occurence of excessive wear ofthe brake pads 69, 71. Such excessive wear is indicated by an excessiveangular movement of the yoke lever 63 and thus an excessive linearmovement of the control rod 76 during a brake operation.

An anti-rattle spring 79 is provided between the adjuster 73 and thefixed part 61.

Numerous modifications are possible within the scope of the appendedclaims, for example regarding the type of slack adjuster and brakecylinder used, as well as regarding their positions. Especially it is tobe noted that, although in the FIGS. 1-4 embodiments the yoke lever isshown as a substantially straight arm and the brake cylinder is mountedon the end of the yoke opposite the disc, a curved yoke lever and abrake cylinder mounted on the side of the yoke may be a good solutionunder certain circumstances.

We claim:
 1. A rail vehicle arrangement for braking at least one disc,comprising in combination a disc brake yoke with two telescoping yokeparts to be suspended from an underframe of the vehicle in the vicinityof the disc to be braked, two pad holders with corresponding brake padspositioned on either side of the disc, a slack adjuster arranged to actbetween said two telescoping yoke parts having a control arm, one ofsaid yoke parts defining a pivot axis intermediate the slack adjusterand the discs, one pad holder with a corresponding brake pad beingmounted on an end of the other said yoke part remote from the slackadjuster, a yoke lever having an intermediate pivot point pivoted onsaid pivot axis with the second pad holder and its brake pad disposed atone end, means attaching the other end of the yoke lever having thepivot point to a brake operating cylinder mounted on said yoke partdefining a pivot axis for operation of the brake pads, and meansoperating the slack adjuster control arm with movements of the yokelever to control the slack adjuster.
 2. A disc brake arrangementaccording to claim 1 with a control member protruding from the slackadjuster, characterized in that the slack adjuster is of the axial type,is arranged within the yoke, is attached to the second yoke part and isanchored to the first yoke part so that the yoke lever coacts with saidcontrol member protruding from the slack adjuster.
 3. A rail vehiclearrangement for braking at least one disc, comprising in combination adisc brake yoke with two telescoping yoke parts to be suspended from anunderframe of the vehicle in the vicinity of the disc to be braked, afluid operated brake cylinder mounted on said yoke, two pad holders withcorresponding brake pads positioned on either side of the disc, a slackadjuster arranged to act between said two telescoping yoke parts,namely, a first part and a second part on the yoke, one pad holder witha corresponding brake pad being mounted on the first yoke part, a yokelever carrying the second pad holder and its brake pad, means pivotallyattaching the yoke lever at an intermediate portion thereof to thesecond yoke part, means attaching the yoke lever to the cylinder foroperation of the brake pads, and means operating a slack adjustercontrol arm with the yoke lever to control the slack adjuster whereinthe slack adjuster is attached on the second yoke part and is of theautomatic brake lever type primarily intended for automotive S-cam drumbrakes, with a worm wheel connected to a cam-shaft rotatably arranged inthe second yoke part, and a cam on the cam-shaft engaging acorresponding hole in the first yoke part.
 4. A disc brake arrangementaccording to claim 3, characterized in that a control arm on the slackadjuster is connected to a transmission lever arm pivotally attached tothe yoke lever.
 5. A rail vehicle arrangement for braking at least onedisc, comprising in combination a disc brake yoke with two telescopingyoke parts to be suspended from an underframe of the vehicle in thevicinity of the disc to be braked, a fluid operated brake cylindermounted on said yoke, two pad holders with corresponding brake padspositioned on either side of the disc, a slack adjuster arranged to actbetween said two telescoping yoke parts, namely, a first part and asecond part on the yoke, one pad holder with a corresponding brake padbeing mounted on the first yoke part, a yoke lever carrying the secondpad holder and its brake pad, means pivotally attaching the yoke leverat an intermediate portion thereof to the second yoke part, meansattaching the yoke lever to the cylinder for operation of the brakepads, and means operating a slack adjuster control arm with the yokelever to control the slack adjuster wherein the brake cylinder isconnected to the yoke lever at its connection to the pad holder with itsbrake pad, and having an arm on the lever acting as a control means forthe slack adjuster.